1. Field of the Invention
The present invention relates to a biaxially oriented, laminated polyester film particularly suitable as a base film for video tapes.
2. Description of the Related Art
As a biaxially oriented polyester film used as a base film for magnetic recording media, a film containing spherical silica particles originating from colloidal silica is known and described in, for example, JP-A-SHO 59-171623. Further, as a biaxially oriented, laminated polyester film, a polyester film, wherein a thin layer containing particles to form surface protrusions is laminated on a base layer, is also known and described in, for example, JP-A-HEI 2-77431.
In such conventional polyester films, however, there is a problem that a film surface, particularly, protrusions formed on the film surface, is likely to be abraded by a contacting roll or guide or an edge of an applicator, particularly accompanying with recent increase of a tape or film running speed in FF and REW modes of a video tape recorder, a calendering or applying process for making magnetic recording media, a dubbing process, or a process for incorporating a tape into a cassette. Further, there is a problem that the signal/noise ratio (S/N) when the film is processed into a sufficiently high-quality image when the original video tape formed from the film is dubbed particularly at a high dubbing speed which has been realized by a high-speed magnetic field transferring technology.